1. Field of the Invention
The present invention relates to a double wishbone type front suspension apparatus. In particular, the present invention relates to a double wishbone type front suspension apparatus for a saddle ride type all terrain vehicle such as a four wheel buggy.
2. Description of Background Art
Japanese Examined Utility Model Publication No. H7-23285 discloses a double wishbone type front wheel suspension apparatus of a four wheel buggy. According to the above front wheel suspension apparatus, suspension arms pivotably attached to a vehicle body are arranged in an upward and downward manner. Furthermore, a knuckle is attached to outer ends of the respective arms via ball joints and a knuckle arm provided to the knuckle and a steering arm extending from a lower end of a steering shaft are connected by a tie rod. In addition, the tie rod is arranged on rear sides of the suspension arms in plan view. Furthermore, by bending a rear side of an upper arm provided on an upper side of the suspension arms to a lower side and passing the tie rod by utilizing the bent portion, interference between the tie rod and the upper arm is avoided.
FIG. 7 of the present invention illustrates a plan view of an upper arm constituting another embodiment. According to this embodiment of the upper arm, by connecting a front pipe 1 and a rear pipe 2 substantially in a V shape and connecting middle portions of the two pipes by a cross pipe 3, the upper arm is referred to as an A arm which constitutes substantially an A shape as a whole. A ring portion 4 is provided at an outer end portion of the upper arm, connected to a knuckle via a ball joint, not illustrated, attached thereto. Furthermore, respective base portions of the front pipe 1 and the rear pipe 2 are respectively provided with a front side vehicle body attaching portion 5 and a rear side vehicle body attaching portion 6 to pivotably attach the upper arm to a vehicle body.
Referring to FIG. 7, a joint center line L is drawn to pass a ball joint center A, constituting the center of the ball joint attached to the ring portion 4, orthogonally to a vehicle center line C in a front and rear direction. Accordingly, the joint center line L intersects with the rear side vehicle body attaching portion 6. Furthermore, a rear end 7 of the rear side vehicle body attaching portion 6 extends rearward from the joint center line L. Furthermore, an attaching center B constituting a center of a cushion attaching portion 8 provided at an upper face of the upper arm is disposed rearward from the joint center line L.
In addition, when the rear portion of the upper arm is bent as in Japanese Examined Utility Model Publication No. H7-23285, mentioned above, it is advantageous, since the tie rod and the upper arm can be arranged proximate to each other. However, the forming of the bent portion is complicated. Accordingly, it is not preferable to provide a bent portion in view of the fabrication thereof.
When the upper arm is constructed as in the example of FIG. 7, it is unnecessary to bend the rear pipe 2. However, in an all terrain vehicle such as a four wheel buggy, it is sometimes desired to increase an up and down stroke of the front wheel suspension apparatus and enlarge the diameter of the front wheel. In this case, if the upper arm of FIG. 7 is used for that purpose, since the joint center line L intersects with the upper arm in plan view, when the up and down stroke of the front wheel is increased, interference of the upper arm with the tie rod may occur. Accordingly, the increase in the up and down stroke is restricted. Furthermore, the tie rod is moved in the front and rear direction during turning. Therefore, depending on a position of the attaching center of the cushion attaching portion, there is also a concern that the tie rod will interfere with the cushion unit.
In addition, when it is desired to enlarge the diameter of the front wheel, a position of the axle must be moved toward the front side. However, when the position of the axle is simply moved to the front side, it becomes necessary to change a position of the steering shaft or an inner side end portion (inner portion of the side of the steering shaft) of the tie rod in order to avoid interference between the upper arm and tie rod. However, the change of the steering shaft causes a change in riding attitude and accordingly, the change is not preferable. Furthermore, on the rear side of the tie rod, there are arranged an engine and accessories thereof. Therefore, the change with regard to the position of the inner side end portion of the tie rod is also not preferable since a large-scale change of the vehicle body layout becomes necessary.
In view of the above, it is an object of the invention to resolve the above problems. In order to resolve the above-described problems, according to a first aspect of present invention, there is provided a front wheel suspension apparatus wherein one end of a suspension arm is pivotably attached to a vehicle body. The front wheel suspension apparatus includes an upper arm and a lower arm separated from each other in an up and down direction. Outer ends of the upper and lower arms are connected via a ball joint by a knuckle which is for supporting a front wheel axle. A knuckle arm provided at the knuckle and a steering arm extended from a lower end of a steering shaft, are connected by a tie rod. Furthermore, a cushion unit is interposed between the upper arm and the vehicle body, wherein the upper arm constitutes substantially a triangular shape in plan view. In addition, a portion of the upper arm, which corresponds with a side of the triangular shape, is attached with a single vehicle body attaching portion continuous in a front and rear direction, which acts as a portion pivotably attached to the vehicle body. A side of one apex portion of the triangular shape opposed to the vehicle body attaching portion, is attached with the ball joint and a cushion attaching portion for connecting a lower end portion of the cushion unit is provided in a vicinity thereof. Furthermore, a rear end portion of the vehicle body attaching portion and an attaching center of the cushion attaching portion are respectively arranged forward from a joint center line passing through a center point of the ball joint and orthogonal to a center line of the vehicle body. In addition, the tie rod is arranged rearward from the joint center line when the tie rod is disposed at a straight line advancing position.
The rear end portion of the vehicle body attaching portion and the attaching center of the cushion attaching portion are respectively arranged forward from the joint center line. Accordingly, even when the front wheel carries out a significant up and down stroke, the rear edge portion of the vehicle body attaching portion and the cushion attaching portion do not interfere with the tie rod. Furthermore, even when the tie rod is moved in the front and rear direction when making a turn, the tie rod does not interfere with the cushion unit. In addition, when it is desired to move the position of an axle forward from a conventional position, even when the tie rod connected to the knuckle arm is advanced along with the axle without changing the position of the steering shaft, the interference with the upper arm can be avoided. The position of the axle can be made movable to the front side without changing inner side positions of the steering shaft and the tie rod.
Accordingly, larger up and down stroke of the front wheel can be ensured without requiring a change in the vehicle riding attitude or a significant change in the vehicle body layout and movement of the position of the axle is facilitated. Therefore, a large diameter formation of the front wheel is facilitated. As a result, there is provided a front wheel suspension apparatus that is preferable for an all terrain vehicle such as a four wheel buggy.